Author: JW de Kort
Date: 02:46:29 12/17/02
Go up one level in this thread
On December 17, 2002 at 04:46:16, Uri Blass wrote: >On December 17, 2002 at 04:27:48, JW de Kort wrote: > >>On December 17, 2002 at 03:40:11, Uri Blass wrote: >> >>>I think to add to my program bitboard that will be used only for pawn structure. >>> >>>2 numbers of 64 bits that are used for white pawns and for black pawns. >>> >>>I want to detect based on these bitboards a lot of information about every pawn >>>and I may want to use the information together with attack tables for >>>evaluation. >>> >>>My question is if using bitboard is a good idea to get the information and >>>if the answer is positive how can I detect the information by bitboards >>> >>>For every pawn I want to detect the following: >>> >>>1)Is it a weak pawn(a pawn that can never be defended by a pawn and cannot go >>>forward to promote without captures and without the risk of being captured by a >>>pawn) >>>2)Is it probably weak pawn(it means that the only way to defend it by a pawn is >>>by capturing the opponent pawn or by letting the opponent to capture the >>>potential defender by a pawn). >>> >>>3)Is it a pawn that is defended by a pawn and if not how many normal pawn moves >>>that are not captures and do not let the opponent to capture by a pawn are >>>needed to defend it by a pawn. >>> >>>4)Is it a passed pawn and if it is a passed pawn how many normal pawn moves are >>>needed to defend it by a pawn. >>> >>>5)Is it a potential passed pawn(is the only way of the opponent to stop it is by >>>letting the player to have another passed pawn) >>>In case that it is a potential passed pawn the question is if it can be done by >>>normal means or the only way to make it a passed pawn is by sacrifices >>> >>>Uri >> >>Dear Uri, >> >>I do this in my 0x88 based program: i use bitboards to do the pawn evaluation. >>This evaluation is only on a very basic level but the topics you mention is >>covered. I found out that by bitboard it is far easier and quicker to check >>whether a pawn is passed or not but i think this is commom knowledge. I found >>the source of Crafty very informative. >> >>regards >> >>Jan Willem > >1)This seems to be not very basic level. > >In the match steve ham against computers Nimzo7.32 could not evaluate correctly >a black passed pawn at c3 that could not be protected by a pawn and gave it a >big bonus. > >If even Nimzo7.32(that is at the level of the top amateurs) could not evaluate >it then it means that it is not a basic evaluation because I expect nimzo7.32 to >know at least everything that is very basic level. > >I guess that big majority of the chess programs do not have this information >because most amateurs have less knowledge than nimzo7.32(movei of today even >does not evaluate passed pawns). > I'am afraid my response was not completely clea at this point or maybe i got your question not right. M<y progrma can tell if a pawn if passed atc. by using bitboards but iám not to say that it is evaluated correctly. My engine is very weak at the moment and one of the problems is the wrong evaluation of these features. I understood your question as; how to detect these things. Iám sorry if i under estimated you. (I wonderde why you asked this question to be honest). By 'basic' i mean that an evaluationfunction coveres all the aspectes that are already in the function of CHESS 4.5. >2)Where did you look at crafty source code to find the relevant information that >helped you? I took a close look in the evaluationfunction where the pawns are evalutaed. But i think it is not to hard to understand this. e.g if you want to know if a pawn is passed you can do a logical AND with the bitboard of all opposite pawns and an bitboard giving all the squares that must be empty for the pawn to be passed. (Again i appologize if this information is not what you are looking for). > >Note that I plan to use the information for the evaluation but it does not mean >that this information will give me the evaluation because I want to evaluate >weak pawn that is attacked by the opponent as less than weak pawn that is not >attacked by the opponent so I may use my attack tables. > >3)What is the level of your program? > Not very good i'am afraid. The evaluationfunction does know almost all the features of CHESS 4.5 like passed pawns, backwardspawns, very backwardspawns, doubled rooks, rooks and quens on seventh rank, kin safety, caslte bonus for being casteld and a malus for not being so, king tropism, center tropism, placement of pieces like near the centre and on safe squares etc. but these features are at the moment so badly tuned that my program is willing to open up his king defence to advance his pawns. But again this is only for starters, since it can play under winboard iám planning to make it stronger. My main concern however is the speed, or better the lack of it. I saw it beat BEOWULF once but i saw it beaten by BEOWULF about twenty times. It largely depends on the opening my progrma plays if it can give some resistance. >Uri
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